As disclosed in U.S. Pat. No. 3,808,296 (Bruneni), 3,927,150 (Schwarzenbach et al.), U.S. Pat. No. 4,305,866 (York et al.), and U.S. Pat. No. 4,371,647 (Minagawa et al.), it is known that many phosphorus compounds, including some aromatic phosphites having a cyclic caged structure, have been found to be useful as stabilizers for organic materials which are normally susceptible to oxidative deterioration and that they are frequently particularly useful in this regard when employed in conjunction with phenolic antioxidants.
It is also known, however, that some phosphites have been discovered to be unsatisfactory for use as antioxidants because of lacking good overall stabilizing ability, contributing color to polymeric materials in which they have been incorporated, and/or being thermally or hydrolytically unstable.
Kirpichnikov et al., Russian Chemical Reviews, Vol. 52 (11), 1983, pp. 1051-1063, teach that effective stabilization of polymers can be achieved by the use of synergistic mixtures of phosphites having different types of activity, i.e., inhibition of radical processes (a sterically-hindered aromatic phosphite) and serving as an acceptor of molecular polymer reaction products (aliphatic and mixed alkyl aryl phosphites).
In a different field of endeavor, phosphorus compounds are of interest as potential replacements for halogen compounds as flame retardants for normally flammable organic materials because of the hazards involved in the use of the halogen compounds. Known phosphorus compounds have been found to be generally inferior to the halogen compounds, especially the bromine compounds, which have been the flame retardants of choice for many organic polymers; and it would therefore be advantageous to discover new phosphorus compounds which might be superior to the known phosphorus compounds in this regard.